using namespace std;
#include <iostream>
#include <string>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main()
{
    // 1. 创建管道
    int fds[2] = {0};
    int n = pipe(fds);
    if(n != 0)
    {
        cerr << "pipe error" << endl;
        return 1;
    }
    // Father process -> read
    // Child process  -> write 
    // 2. 创建子进程
    pid_t id = fork();
    if(id < 0)
    {
        cerr << "fork error" << endl;
        return 2;
    }
    else if(id == 0)
    {
        // 子进程
        // 3. 关闭不需要的fd,关闭read
        close(fds[0]);
        int cnt = 0;
        while(true)
        {
            string message = "hello world, hello ";
            message += to_string(getpid());
            message += ",";
            message += to_string(cnt);

            // fds[1]
            ::write(fds[1], message.c_str(), message.size());
            cnt++;
            sleep(1);

            break;
        }
        exit(0);
    }
    else
    {
        // 父进程
        // 3. 关闭不需要的fd, 关闭write
        close(fds[1]);
        char buffer[1024];
        while(true)
        {
            ssize_t n = ::read(fds[0], buffer, 1024);
            if(n > 0)
            {
                buffer[1024] = 0;
                cout << "child -> father, message: " << buffer << endl;
            }
            else if(n == 0)
            {
                // 如果写端关闭
                // 读端读完管道内部的数据，在读取的时候，就会读到返回值0
                // 表示对端关闭，也表示读到了文件末尾
                cout << "n: " << n << endl;
                cout << "child quit? me too" << endl;
                break;
            }
        }

        pid_t rid = waitpid(id, nullptr, 0);
        cout << "father wait child success:" << rid << endl;
    }



    return 0;
}
